1. Field of the Invention
The present invention pertains generally to the field of load lifting devices and is more particularly directed to a jack system suitable for lifting and temporarily supporting roof mounted air conditioning equipment away from the roof surface so as to permit access for repair of the underlying roof area.
2. State of the Prior Art
It is common practice in the construction industry to mount the heat exchanger units of central air conditioning systems on the roof of the building where ambient air is blown through the unit for cooling purposes. The usual installation consists of simply resting the air conditioning unit on a pair of wooden blocks, called runners, or similar spacers placed on the roof surface. Such arrangements are particularly common in buildings having flat, level roofs. This type of roof is typically weather-proofed by one or more layers of tar paper and asphalt, or equivalent impermeable sheet material, which in time develops cracks and open seams along overlapping edges of the roofing material so that rain water leaks through the roof, therefore requiring periodic maintenance and repair. Eventually, as the roofing material ages, localized patching and minor repairs no longer suffice to maintain the integrity of the roof and complete re-roofing becomes necessary. Re-roofing involves the laying down of fresh tar paper or the like over the old roofing material and waterproofing all joints and seams with hot, liquid asphalt. Roofing material such as tar paper is bought in rolls which are unrolled on the roof surface as relatively long parallel strips of roof covering until the desired area has been covered. Irregular portions of the roof are then individually treated with pieces of roofing material cut and laid down as required.
A recurring problem in re-roofing jobs is the presence of roof mounted air conditioning equipment arranged on the roof without regard for the eventual need to gain access under those units for roof maintenance and repair.
The air conditioning units are usually not fastened down to the roof and merely rest on spacers or supports high enough to keep the unit above rain puddles and out of contact with the tar and asphalt roof covering, leaving very little clearance between the air conditioning unit and the roof surface for purposes of roof repair. The clearance under the air conditioning unit is typically three and a half inches due to the common use of 4.times.4 wooden runners as supports for this purpose. In order to obtain adequate access to the roof area under such air conditioning units, it is desirable to raise the unit by at least an additional four to five inches so that it is supported at least 8-9 inches above the roof surface while the wooden supports are pulled out and new roofing material laid under the raised unit.
The present approach is to lift the air conditioning equipment, often weighing hundreds of pounds, with makeshift levers made of 2.times.4 timer or with crowbars which frequently damage the air conditioning unit or the associated sheet metal duct work and electrical conduits. No convenient, low cost, work saving system is known for dealing with this problem and a continuing need exists for a simple, safe and effective device for quickly and easily lifting and supporting roof mounted air conditioning units or other roof mounted equipment while repair or re-roofing work is carried out under the raised unit.